Ammonium ions generation

The principal side reaction to epoxide coupling is hydrolysis. Particularly at acid pH values, the epoxide ring can hydrolyze to form adjacent hydroxyls. This diol can be oxidized with periodate to create a terminal aldehyde residue with loss of one molecule of formaldehyde (Chapter 1, Section 4.4). The aldehyde then can be used in reductive amination reactions. The reaction of an epoxide group with an ammonium ion generates a terminal primary amine group that also can be used for further derivatization. 

Keto acid (170) has been transformed into the diastereomeric mixture of keto acids (171) and (172), where the predominant reaction pathway involves approach of the electrophile anti to the carboxylate group (Scheme 31). It was found to be essential to neutralize the ammonium ions generated from addition of the substrate acid to the liquid ammonia before adding the potassium metal, however. ... 

The rate enhancements by (5) were larger than those found with the micelle forming surfactant, CTACl [123], and it was suggested that the quaternary ammonium ion generated hydrophobic ion pairs which were very good nucleophiles. 

Reeves and coworkers have recently published examples of tertiary amine catalyzed nitrile formation [29], thiocyanate formation [30], alkylation [31], and carbene formation [31 ]. These reactions almost certainly involve catalysis by quaternary ammonium ions generated in situ. 

Figure 5 illustrates the effect the urea in concentration from 10 to 10 mol/1 produces on fluorescence spectra of capsules containing SNARF-1 dextran and urease. Urea concentration dependence is reflected spectroscopically by apparent pH change in the course of enzymiatic reaction inside the capsules. The ammonium ions generated via enzymatic reaction in capsule interior effect on pH shift what is recorded by SNARF-1 on the plot (Fig. 5). The fluorescent spectra were measured at the 30-min time point after adding urea solutions at these concentrations to the SNARF-1 dextran/urease capsule s samples. Our particular attention was paid to the kinetics of the change at the fluorescence intensity ratio at 580 nm to 640 nm R (Fig. 6) and its relevance to amount of SNARF/urease. Parameter R was plotted versus time and as one can see on curves at high concentration...

An important extension of these reactions is the Mannich reaction, in which aminomethyl-ation is achieved by the combination of formaldehyde, a secondary amine and acetic acid (Scheme 24). The intermediate immonium ion generated from formaldehyde, dimethyl-amine and acetic acid is not sufficiently reactive to aminomethylate furan, but it will form substitution products with alkylfurans. The Mannich reaction appears to be still more limited in its application to thiophene chemistry, although 2-aminomethylthiophene has been prepared by reaction of thiophene with formaldehyde and ammonium chloride. The use of A,iV-dimethyf (methylene) ammonium chloride (Me2N=CH2 CF) has been recommended for the iV,iV-dimethylaminomethylation of thiophenes (83S73). 

The sensor is an ammonium ion-selective electrode surrounded by a gel impregnated with the enzyme mease (Figme 6-11) (22). The generated ammonium ions are detected after 30-60 s to reach a steady-state potential. Alternately, the changes in the proton concentration can be probed with glass pH or other pH-sensitive electrodes. As expected for potentiometric probes, the potential is a linear function of the logarithm of the urea concentration in the sample solution. 

Just as there are weak acids, there are also weak bases. A weak base does not readily accept protons from water molecules but does quantitatively accept protons from hydronium ions. Ammonia is the most common weak base. Ammonia exists predominantly as NH3 molecules in aqueous solution, but it undergoes quantitative proton transfer with hydronium ions to generate ammonium ions ... 

Enzyme sensors are based primarily on the immobilization of an enzyme onto an electrode, either a metallic electrode used in amperometry (e.g., detection of the enzyme-catalyzed oxidation of glucose) or an ISE employed in potentiometry (e.g., detection of the enzyme-catalyzed liberation of hydronium or ammonium ions). The first potentiometric enzyme electrode, which appeared in 1969 due to Guilbault and Montalvo [140], was a probe for urea with immobilized urease on a glass electrode. Hill and co-workers [141] described in 1986 the second-generation biosensor using ferrocene as a mediator. This device was later marketed as the glucose pen . The development of enzyme-based sensors for the detection of glucose in blood represents a major area of biosensor research. 

Zhang s group [82] recently presented a novel CL sensor combined with FIA for ammonium ion determination. It is based on reaction between luminol, immobilized electrostatically on an anion-exchange column, and chlorine, electrochem-ically generated online via a Pt electrode from hydrochloric acid in a coulometric cell. Ammonium ion reacts with the chlorine and decreases the produced CL intensity. The system responds linearly to ammonium ion concentration in a range of 1.0-100 pM, with a detection limit of 0.4 pM. A complete analysis can be performed in 1 min, being satisfactorily applied to the analysis of rainwater. 

Figure 3 shows the cathodic reaction. The counter ion, protonated trialkyl ammonium ion, migrate through the ion selective membrane to the cathode. Hydroxyl ions are generated at the cathode where they reduce the amine ions to free amines. 

To abstract a proton is to remove only the proton. The substantial extent of dissociation in Equation (6.11) helps explain why aqueous ammonia is more properly called ammonium hydroxide , NH4OH. We generate the solvated hydroxide ion OH (aq) by abstracting a proton from water. The OH (aq) ion in Equation (6.11) is chemically and physically identical to the solvated hydroxide ion generated by dissolving NaOH or KOH in water. 

Quaternary fluorinated alkyl ammonium compounds The fluorine-containing cationic surfactants of quat type with the general formula C F2 , 1-S02-NH-CH2-CH2-CH2-N (CH3)3 X (n = 8) (Fig. 2.12.1(d)) were examined by FIA—MS using APCI and ESI in the positive and negative modes. The APCI(- -/—) ionisation resulted in a dealkylation at the nitrogen with ions at m/z 585 or 583, respectively. The alkyl chain of this compound contained the moiety C8Fi7. The ions generated under APCI conditions were characterised as dealkylation products—m/z 585 [M — CH2]+ or m/z 583 [M — H— CH3] —as reported in the literature [35,37]. 

The two ammonium ions produced from glutamine as illustrated in Figures 8.4 to 8.6 are secreted into the PCT lumen the by a Na+/H+ antiport (the NH4+ substitutes for H+). Subsequent metabolism of 2-oxoglutarate has the potential to generate two bicarbonate ions from the hydration of carbon dioxide by carbonic anhydrase ... 

The starting material was prepared with the modification on the epibatidine bicychc ring system by repositioning the nitrogen atom to a methylene group. We carried out the Hetero-Diels Alder reaction of cyclopentadiene and iminium ion generated from ammonium chloride and formaldehyde in the aqueous medium and protected resulted unstable secondary amine with benzoyl chloride to provide (3) in good yields [5] (Scheme 38.1). 

CASRN 56-40-6 molecular formula C2H5NO2 FW 75.07 Chemical/Physical Products identified from the oxidation of glycine and OH radicals (generated from H2O2/UV) in oxygenated water were oxalic acid, formic acid, and ammonium ions. In oxygen-free water, oxalic and formic acids were not produced, i.e., glycine oxidized directly to ammonium ions. The rate constant for the reaction of OH radicals with the zwitterion ion is 1.7 X 10 /M-sec and with the anionic form is 1.9 x 10 /M-sec (Vel Leitner et al., 2002). 

Rabbits form bicarbonate in the gut and absorb it. They do not have to form new bicarbonate in the kidneys and need not excrete ammonium ions in the urine, but they still need to excrete organic anions. These organic anions are accompanied in the urine by sodium or potassium ions, which can generate a severe negative sodium balance for the period that the rabbits are on a browse diet(Iason and Palo, 1991). Therefore, lagomorphs excrete biotransformational... 

C. Preparation. As indicated by the E-pH diagram, the ammonium ion NH4+ can be prepared by acidifying a basic solution of NH4OH (actually hydrated NH3) until a pH of 9.2 or below is attained. The counterion (anion) associated with the NH4 is determined by the anion of the acid used in the acidification. The precursor of NH4 , namely NH3, is produced by the reaction of N2 with H2 at an elevated temperature in the presence of a catalyst. The H2 for this reaction is generated from various substances including coke and natural gas (CH4). 

Infrared and Raman spectroscopy. Stephens and Price (1970, 1972) used infrared spectroscopy to examine both ambient and laboratory-generated aerosols. They identified sulfate, nitrate, and ammonium ion absorption bands in ambient particles as well as bands indicating the presence of organics in diesel exhaust (C-H) and oxidized organics in irradiated hydrocarbon-NO, . mixtures. Since then, many studies using IR have been carried out and a variety of species identified, including COf , PO4-, and SiO A See Chapter 9.C.2 and Figs. 9.49, 9.50, and 9.51 for some typical FTIR spectra of atmospheric particles. 

Furthermore, in the manufacture of zeolite catalysts, ion exchange plays an outstanding role. Bronsted acid sites can be readily generated by introducing ammonium ions followed by a heat treatment or by introducing multivalent metal cations, again followed by heat treatment (Weitkamp, 2000). However, not all these applications incorporate the ion exchange and catalysis phenomena at the same time, i.e. simultaneous action of these two mechanisms. 

Alkyl halides can be converted to symmetrical ethers by treatment with oxide ion generated in situ by a reaction between an organotin oxide and fluoride ion in the presence of a quaternary ammonium iodide or a crown ether.715... 

---